Light-filtering overcoating



Patented 1mg. 7, 1934 I 1,969,473 LIGHT-FILTERING OVERCOATING Thomas F. Murray, .ln, Rochester, N. Y assignor to Eastman Kodak Company, Rochester, N. Y a corporation of New York No Drawing. Application January 16, 1932,

Serial No. 587,162

15 Claims.

This invention relates to protective coatings and to articles coated therewith. One of its objects is to provide a filter for the absorption of ultra-violet light. Another object is to provide a 5 lacquer or overcoating which absorbs substantially all the ultra-violet light which would have a deleterious effect upon the underlying surface. Another object is to provide a cellulose acetate lacquer which, having been applied over a nitrol0 cellulose lacquer, absorbs many of the light rays which have a decomposing effect upon nitrocellulose.

It is a well known fact that nitrocellulose lacquers lose their gloss with relatively great rapidity when exposed to the elements. The delustering and decomposition of nitrocellulose lacquer surfaces, while to some extent due to inclement weather conditions, is primarily due to the ultra-violet rays from the sun, which penetrate and decompose the surface layer.

While the addition of pigments and plasticizers to nitrocellulose compositions aids to a slight extent in rendering a nitrocellulose layer used as an outer coating less afiected by ultra-violet light, the protection they afford is not by any means complete. Even with a considerable amount of these constituents present in the lacquer, there is, nevertheless, upon the surface, a goodly proportion of cellulose nitrate directly exposed to the solar radiation. Moreover, it has been found thatunder such conditions the exposed cellulose nitrate will be decomposed by ultra-violet light falling upon its surface.

It has previously been proposed to protect cellulose nitrate lacquers from ultra-violet light by overcoating them with cellulose acetate lacquers. Cellulose acetate of itself does, not decompose appreciably under the influence of ultra-violet light. However, it will not fully protect an under layer 40 of cellulose nitrate over which it may be coated,

forthe reason that it does not completely absorb those light rays which decompose the nitrate. When, however, small quantities of certain substances which themselves have the property of absorbing ultra-violet light are incorporated in cellulose acetate lacquer compositions, the coatings produced from theslacquers are very efiective in protecting underlying nitrocellulose coatings from ultra-violet light.

I have discovered that cellulose acetate compositions which contain small percentages of triphenyl compounds of the elements in subgroup B of group V of the periodic table have the property of inhibiting the passage of ultraviolet light. These compounds are triphenyl bismuthine, triphenyl stibine, triphenyl amine, triphenyl arsine and triphenyl phosphine. They have all been described in the literature. When added to cellulose acetate lacquers in amounts of from approximately 2% to 5% or more based so on the weight of the cellulose acetate, they effectively protect from ultra-violet light a nitrocellulose or other surface overcoated with the cellulose acetate lacquer.

It is not particularly material what type of vehicle holds the filter, as suitable varnishes, gums, waxes, shellacs, etc. are for some purposes as useful as cellulose acetate as vehicles in which to incorporate the filter. Nor should I be understood to restrict myself to cellulose acetate specifi- 70 cally as a cellulose derivative vehicle for a lightfiltering overcoating. There are numerous other esters of cellulose, suchas cellulose propionate, cellulose butyrate, cellulose acetate-propionate, cellulose acetate-benzoate, cellulose nitro-acetate, cellulose phospho-acetate, etc., many of which are useful as vehicles in which to incorporate the filter for use as an overcoating. In selecting the vehicle it must, of course, be home in mind that only those substances are suitable which are themselves not as rapidly decomposed as the subcoating which they are used to protect.

My novel overcoating lacquers may be prepared in the following manner, although any method which uniformly disperses the light-filtering substance throughout the vehicle used may generally be employed. Cellulose acetate, for example, may be mixed with approximately 3% of its weight of the triphenyl compound of an element in subgroup B of group V of the periodic table, for instance' triphenyl amine, with or without the addition of say up to 50% of a suitable plasticizer. This mixture may then be dissolved in a suitable solvent or solvent mixture, such as one made up of 15% ethyl acetate, 50% acetone, 20% ethyl lactate and 15% denatured alcohol, approximate ly one gallon of this solvent being required for 20 ounces of cellulose acetate. This example is given merely to acquaint those skilled in the art with one manner of incorporating the filter, and I am not to be limited by the details or proportions of this example except as may be indicated by the appended claims.

The term overcoating, and the description of these overcoatings in connection with lacquers, are to be understood broadly rather than specifically, as it will be apparent that the value of my invention lies in the fact that by interposing, between the cellulose nitrate layer and the source of the ultra-violet rays, a vehicle containing the no ultra-violet light filter,the nitrate underlayer will be protected from decomposition and deterioration. Thus, the cellulose acetate overcoating may consist of an already formed sheet containing the 5 filter, which sheet is interposed between the cellulose nitrate sheet to be protected and the source of the ultra-violet light. Furthermore, in the case of laminated glass, for instance, the cellulosederivative reinforcement interposed between the glass laminations may consist of a cellulose nitrate interlayer on either side of which is coated, or otherwise imposed, alayer or. coating of a vehicle such as cellulose acetate with which has been incorporated an ultra-violet light filter. Thus, even though the cellulose nitrate interlayer be covered on both sides with glass, it is first covered with a vehicle containing an ultra-violet alight filter, scthat the cellulose nitrate is protected from decomposition by the ultra-violet light which would otherwise'penetrate the cellulose .nitrateanddecompose it. Thus, the term overcoating used in this specification and the appended claims is not to be confined toa mere lac- I adhering coating decomposable by sunlight, and I Uquertop coat, but is to beconstrued broadly as any shielding layer containing an ultraviolet filter for preventing decomposition of cellulose nitrate by ultra-violet light, or for protecting any surface or substance from ultra-violet light.

' What I claim as my invention and desire to be secured by Letters Patent of the United States is:

1. An article of manufacture having a closely adhering coating. decomposable by sunlight, and a light fitering overcoating comprising an organic derivative of cellulose and the triphenyl com pound of an element of sub-group B of group V of the periodic table.

2. An article of manufacture having a closely a light filtering overcoating comprising an organic derivative of cellulose and triphenyl amine.

6. Anfarticleof manufacture having a closely adhering coating decomposableby sunlight, and

a light filtering overcoating comprising cellulose acetate and triphenyl bismuthine.

7. An article of manufacture having a closely adhering,coatingdecomposable by sunlight, and

a light filtering overcoating comprising cellulose acetate and triphenyl stibine.

8. An article of manufacture having a closely adhering coating decomposable by sunlight, and

a light filtering overcoating comprising cellulose k acetate and triphenyl amine. 9. An article cii manufacture having a closely adhering coating decomposable by sunlight, and

a light filtering overcoating which comprises cellulose acetate, the triphenyl compound of an elementof sub-group B'of group V of the periodic table, and a plasticizer.

filtering protective covering comprising a cellulose acetate overcoating superimposed upon a cellulose nitrate coating, the overcoating, due to itscontentofthe triphenyl compound of an element of sub-group B of group V of the periodic table, havmg the characteristic that it absorbs substantially all theultra-violet that reaches the g earth's surface from the sun, and thereby protects the cellulose nitrate coating-from decomposition.

11: An article of ,manufacturehaving a cellulose nitrate coating with an overcoating of cellulose acetate containing the triphenyl compound- I of an element of sub-group B of. group V or the periodic table.

12. An article of manufacturehaving' a cellu lose acetate containing triphenyl bismuthine.

' v 13. An article of manufacture havinga cellulose nitrate coating with an overcoating of cellulose acetate containing triphenyl stibine. l 14. An article of manufacture having a cellulose nitrate coating with an overcoating 01' cellulose acetate containing triphenyl amine.

' 15. An article of manufacture having a cellulose nitrate coating with an overcoating of cellulose acetate containing from approximately 2% to 5%, the triphenyl compound 01' an'element of subgroup B of group V 01 the periodic table.

moms F. MURRAY, an.

lose nitratecoating with an overcoating of cellu I based on the weight of cellulose acetate, oi.

95' 10. An article of manufacturehaving a light I I 

